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All exceptions reveal information that can assist an attacker's efforts to carry out a denial of service (DoS) against the system. Consequently, programs must filter both exception messages and exception types that can propagate across trust boundaries. The following table lists several problematic exceptions.
Exception Name | Description of Information Leak or Threat |
|---|---|
| Underlying file system structure, user name enumeration |
| Database structure, user name enumeration |
| Enumeration of open ports when untrusted client can choose server port |
| May provide information about thread-unsafe code |
| Insufficient server resources (may aid DoS) |
| Resource enumeration |
| Underlying file system structure |
| Owner enumeration |
| DoS |
| DoS |
Printing the stack trace can also result in unintentionally leaking information about the structure and state of the process to an attacker. When a Java program that is run within a console terminates because of an uncaught exception, the exception's message and stack trace are displayed on the console; the stack trace may itself leak contain sensitive information about the program's internal structure. Consequently, command-line programs any program that may be run on a console accessible to an untrusted user must never abort because of due to an uncaught exception.
Noncompliant Code Example (Leaks from Exception Message and Type)
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This compliant solution operates under the policy that only c:\homepath\file1 and c:\homepath\file2 are permitted to be opened by the user. It also catches Throwable, as permitted by exception ERR08-J-EX2(see ERR08-J. Do not catch NullPointerException or any of its ancestors). It uses the MyExceptionReporter class described in ERR00-J. Do not suppress or ignore checked exceptions, which filters sensitive information from any resulting exceptions.
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Exceptions may inadvertently reveal sensitive information unless care is taken to limit the information disclosure.
Rule | Severity | Likelihood | Remediation Cost | Priority | Level |
|---|---|---|---|---|---|
ERR01-J | Medium | Probable | High | P4 | L3 |
Automated Detection
| Tool | Version | Checker | Description |
|---|---|---|---|
| Parasoft Jtest |
| CERT.ERR01.ACPST CERT.ERR01.CETS CERT.ERR01.ACW | Do not call the 'printStackTrace()' method of "Throwable" objects Catch all exceptions which may be thrown within Servlet methods Avoid writing to Consoles | |||||||
| SonarQube |
| S1989 | Exceptions should not be thrown from servlet methods |
Related Vulnerabilities
CVE-2009-2897 describes several cross-site scripting (XSS) vulnerabilities in several versions of SpringSource Hyperic HQ. These vulnerabilities allow remote attackers to inject arbitrary web script or HTML via invalid values for numerical parameters. They are demonstrated by an uncaught java.lang.NumberFormatException exception resulting from entering several invalid numeric parameters to the web interface.
CVE-2015-2080 describes a vulnerability in the Jetty web server, versions 9.2.3 to 9.2.8, where an illegal character passed in an HTML request causes the server to respond with an error message containing the text with the illegal character. But this error message can also contain sensitive information, such as cookies from previous web requests.
Related Guidelines
VOID ERR12-CPP. Do not allow exceptions to transmit sensitive information | |
CWE-209, Information Exposure through an Error Message |
Bibliography
9.1, Security Exceptions | |
| \[Gotham 2015\] | JetLeak Vulnerability: Remote Leakage Of Shared Buffers In Jetty Web Server |
| [Schönefeld 2004] |
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